The present invention broadly relates to vehicular pneumatic tires and pertains, more specifically, to a new and improved radial-ply tire for use on trucks, particularly for the driving axle or shaft.
Generally speaking, the radial-ply tire of the present development is of the type having a tread profile comprising an equatorial line, a tread-profile width and a plurality of rows of blocks distributed across the tread-profile width and separated from one another by circumferential grooves. The plurality of rows of blocks comprise a central row of blocks extending substantially along the equatorial line, two flanking rows of blocks located one at each side of the central row of blocks, and two lateral rows of blocks extending at respective shoulders of the tread profile. The individual blocks in each row of blocks are separated from each other by cross or transverse grooves having a straight center-line.
For modern radial-ply tires for use on cargo trucks, motor freight cars, lorries and the like, particularly tires for the driving axle or shaft, always more stringent requirements have to be met with respect to safety and economy, i.e. good wear properties. In particular, research and development of such tires must take into consideration the high engine or motor power or output of modern trucks and the commercialized requirement of high mileage of the tire. In this connection, the configuration or structure of the tread profile of such radial-ply tires is of particular importance. For the purpose of improving the mileage of a tire it is to some extent common practice to increasingly augment the depth of the tread profile. However, depending upon the configuration or pattern of the tread profile, this measure can work out unfavorably with respect to stability and handling performance.
Conventional tires for the driving axle or shaft of a truck often comprise a tread profile in which there are provided a plurality of rows of blocks extending in circumferential direction. The circumferential grooves separating these circumferential rows of blocks from one another are thereby structured in zigzagged manner, whereby the zigzag configuration can be at times very pronounced or marked. In direct connection with such configuring or patterning of the circumferential grooves, the individual blocks are configured such that the block edges extending in circumferential direction also comprise an angle-shaped configuration. Longitudinal or straight-course guidance and lateral stability of the vehicle, particularly because of the high engine or motor power and the increased depth of the tread profile, are particularly important requirements. In vehicles provided with driving-axle tires structured as described hereinbefore, the driving axle or shaft tends to laterally drift or deviate from course because of inadequate longitudinal or straight-course guidance. A further problem which can arise in connection with tires having a tread profile with circumferential rows of blocks and showing advanced abrasive wear, is the formation of a so-called sawtooth profile. The leading block edges, i.e. the block edges of the tread profile which, during rolling motion of the tire first come into contact with the ground, are less subject to wear than the second or trailing block edges. The series-arranged blocks in a circumferential row of blocks thus form a substantially sawtooth profile. Furthermore, known driving-axle tires for trucks are worthy of improvement with regard to traction behavior, handling performance, braking and wet-grip properties, particularly on wet or snow covered roadways.